Investigators recruited subjects with chronic cough to undergo continuous and simultaneous monitoring of cough and esophageal reflux. Cough was measured utilizing a custom built sound recording device and reflux was documented using esophageal impedance with pH monitoring. Study participants also underwent bronchoscopy and induced sputum for measurements of airway pepsin.

What They Found

Utilizing these techniques investigators demonstrated that subjects with chronic cough, compared to healthy volunteers as controls:

Demonstrated an increased number of total reflux events (but only slightly: 63.5 vs. 59);

Did not demonstrate any difference in the pH of reflux events

Did not demonstrate a difference in BAL pepsin or sputum pepsin levels.

Moreover, only a small fraction (5.5%) of chronic cough subjects demonstrated "abnormally" increased reflux within their proximal esophagus (>30 events), and this frequency was similar to the healthy controls (5%). Reflux within the proximal esophagus, however, did correlate with sputum pepsin levels when adjusted for cough frequency.

Given that only a small percentage of chronic cough subjects were found to have increased reflux in their proximal esophagus, investigators questioned if GERD is a significant contributor to cough in the majority of chronic cough sufferers.

But reflux of gastric contents into the proximal esophagus is not the only potential causal mechanism for cough, and the authors did not account for these many alternative mechanisms by which GERD can exacerbate or cause cough.

In fact, the authors did appreciate that distal esophageal reflux significantly predicted cough frequency: "abnormal" distal reflux (>73 events) occurred almost four times as often in people with chronic cough (37% of subjects) as in healthy controls (10%).

Taken together, these results support the previously accepted literature that cough and GERD are likely related, and that this relationship is infrequently related to actual micro-aspiration of gastric contents into the airway. Instead, it is probably distal esophageal reflux that is the main contributor to symptoms. The authors have presented an interesting study, with an uninteresting conclusion.